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The maximum normalized beta achieved in long-pulse tokamak discharges at low collisionality falls significantly below that observed in short pulse discharges and that predicted by the ideal magnetohydrodynamic (MHD) theory. Recent long-pulse experiments, in particular those simulating the International Thermonuclear Experimental Reactor (ITER) scenarios with low collisionality v(e)*, are often limited by low-m/n nonideal MHD modes. The effect of saturated MHD modes is a reduction of the confinement time by 10%-20%, depending on the island size and location, and can lead to a disruption. The research focuses on a quantitative comparison between both the conventional resistive and neoclassical theories, and the experimental results of several machines which have all observed these low-m/n nonideal modes. This enables us to single out the key issues in projecting the long-pulse beta limits of ITER-size tokamaks and also discuss possible plasma control methods that can increase the soft beta limit, decrease the seed perturbations, and/or diminish the effects on confinement.

Additional information

Authors: SAUTER O ET AL, CRPP, Association Euratom-Switzerland, PPB-Ecublens, Lausanne (CH);BOUCHER D ET AL, ITER-JCT, La Jolla (US);LA HAYE R J ET AL, General Atomics, San Diego (US);CHANG Z ET AL, Princeton Plasma Physics Laboratory, (US);GATES D A ET AL, AEA Fusion, Culham Laboratory, Abingdon, Oxon (GB);KAMADA Y ET AL, JAERI, Naka-machi, Naka-gun (JP);ZOHM H ET AL, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);BONDESON A, Chalmers University of Technology, Göteborg (SE);CALLEN J D ET AL, University of Wisconsin. Madison (US);HARVEY R W, CompX, Del Mar (US);WAELBROECK F, University of Texas, IFS (US)
Bibliographic Reference: Article: Physics of Plasmas, Vol. 4 (1997) No. 5, pp. 1654-1664
Record Number: 199710931 / Last updated on: 1997-07-23
Original language: en
Available languages: en